package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.RandomUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.RedisConstants;
import com.hmdp.utils.RedisData;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 * 服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    @Override
    public Result queryById(Long id) {
        //缓存穿透
//        Shop shop = queryWithPassThrough(id);
//        互斥锁定义缓冲击穿
//         Shop shop = queryWithMutex(id);
// 使用逻辑过期解决缓存击穿
        Shop shop = queryWithLogicExpire(id);
        if (shop == null) {
            return Result.fail("店铺不存在！");
        }
        return Result.ok(shop);
    }

    public void saveShop2Redis(Long id, Long expireSeconds) {
        //    1.查询店铺数据
        Shop shop = getById(id);
        //    2 封装逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        // 3.写入Redis
        try {
            stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));
        } catch (Exception e) {
            e.printStackTrace();
        }


    }

    public Shop queryWithMutex(Long id) {
        String key = CACHE_SHOP_KEY + id;
//        1 根据id查找对应的店铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
//        2 判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //        3.存在，直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }
//判断命中是否是空值
        if (shopJson != null) {
//返回一个错误信息
            return null;
        }
// 实现缓存重建
//        获得互斥锁
        String lockKey = "lock:shop" + id;
        Shop shop = null;
        try {
            boolean isLock = tryLock(lockKey);
//        判断是否获取成功
            if (!isLock) {
                //        失败，休眠并重试
                Thread.sleep(50);
                return queryWithMutex(id);
            }
//        失败，休眠并重试
//        成功，根据id查询数据库
            shop = getById(id);
//        4.不存在，根据id查询数据库

//        5.不存在，返回错误
            if (shop == null) {
                stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL + RandomUtil.randomLong(5), TimeUnit.MINUTES);
                return null;
            }
//        6.存在，写入redis
            stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
//            7.释放互斥锁
            unLock(lockKey);
        }
//        7.返回
        return shop;
    }


    public Shop queryWithLogicExpire(Long id) {
        String key = CACHE_SHOP_KEY + id;
//        1 根据id查找对应的店铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
//     2 判断是否存在
        if (StrUtil.isBlank(shopJson)) {
            //        3.存在，直接返回
            return null;
        }
//     命中，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        Shop shop = JSONUtil.toBean((JSONObject) redisData.getData(), Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
//     判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
//        未过期，直接返回店铺信息
            return shop;
        }

//        已过期，需要缓存重建

//        缓存重建
        String lockKey = LOCK_SHOP_KEY + id;
//        6.1 获取互斥锁
        boolean isLock = tryLock(lockKey);
//        6.2 判断是否获取锁成功
        if (isLock) {
            //再次检测redis缓存是否过期
            expireTime = redisData.getExpireTime();
//     判断是否过期
            if (expireTime.isAfter(LocalDateTime.now())) {
//        未过期，直接返回店铺信息
                return shop;
            }
            //   成功开启独立线程

                CACHE_REBUILD_EXECUTOR.submit(() -> {
                    //重建缓存

                    try {
                        saveShop2Redis(id, 10L);
                    } catch (Exception e) {
                        throw new RuntimeException(e);
                    } finally {
                        //    释放锁
                        unLock(lockKey);
                    }

                });

        }
//        6.3成功，开启独立线程


//
//        6.存在，写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
//        7.返回
        return shop;
    }


    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    //实现缓存穿透
    public Shop queryWithPassThrough(Long id) {
        String key = CACHE_SHOP_KEY + id;
//        1 根据id查找对应的店铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
//     2 判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //        3.存在，直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }
//判断命中是否是空值
        if (shopJson != null) {
//返回一个错误信息
            return null;
        }

//        4.不存在，根据id查询数据库
        Shop shop = getById(id);
//        5.不存在，返回错误
        if (shop == null) {
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL + RandomUtil.randomLong(5), TimeUnit.MINUTES);
            return null;
        }
//        6.存在，写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
//        7.返回
        return shop;
    }

    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private boolean unLock(String key) {
        stringRedisTemplate.delete(key);
        return true;
    }

    @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        if (id == null) {
            return Result.fail("店铺id不能为空");
        }
//        1.更新数据库
        updateById(shop);
//        2.删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + shop.getId());

        return null;
    }
}
